In general, a filter cloth is configured as a foldable corrugated filter in order to increase dust collection efficiency in a dust collector, and it may be possible to obtain relatively high dust collection efficiency by increasing a surface area of the foldable corrugated filter through a structure thereof.
Meanwhile, when a filter medium, having low rigidity, such as a needle-punched nonwoven fabric and a woven fabric is used as the filter cloth, the filter medium per se may not be held in a corrugated form because of a material thereof having low strength.
Accordingly, in order to hold the filter medium in a corrugated form in the related art, a method is mainly used in which the filter medium is heated and corrugation-formed in a state of containing thermosetting resin such that the corrugated form is fixed to the filter medium. However, there is a problem in that the contained thermosetting resin reduces filterability of the filter for a dust collector.
Meanwhile, a method is already proposed in which opposed portions of the filter cloth are sewn and bonded along a longitudinal direction of the filter cloth in the vicinity of folded portions (a peak portion and a valley portion) in the corrugated form in order to hold the filter cloth in the corrugated form (see Patent Document 1: Korean Unexamined Utility Model Application Publication No. 2010-0007485, published on Jul. 22, 2010).
However, when the conventional filter cloth held in the corrugated form by sewing is used as the filter cloth (back filter) for the dust collector, the filter cloth has a problem in durability.
That is, in the dust collector, the filter cloth is provided, at an inner side thereof, with a retainer in order to be held in a cylindrical shape, and the filter cloth is cleaned by regularly repeated spraying from the inner side thereof using a vibro-method including a pulse jet method, an air blowing method, or a dust removal method.
Accordingly, in a structure of securing the corrugated form of the filter cloth by sewing, the folded portion (inside bent portion in the corrugated form) at the inner side of the filter cloth coming into contact with the retainer is tend to sag as a dust removal process such as pulse jet spraying is repeatedly performed, since the corrugated portion has weaker rigidity compared with a resin processed product. In addition, the corrugated form of the filter cloth may vanish by repeated cleaning to thereby decrease filter efficiency or the filter cloth may be early damaged due to contact with the retainer.
In addition, since the folded portion (peak portion in the corrugated form) at the outer side of the filter cloth does not come into direct contact with the retainer, the filter cloth is not rapidly damaged at the outer side thereof compared with the inner side thereof coming into contact with the retainer. However, the outer side of the filter cloth may be deformed due to blow-bye of strands of thread by the pulse jet and repeated bending, or even damaged due to fatigue.